Traditionally, entities that owned and/or operated software applications also owned the hardware on which the software applications executed. For example, a person may own a copy of an application program and own a personal computer on which the application program may execute. As another example, a company may own a web service and may own computing resources, including hardware resources like one or more servers and/or networking hardware and software resources like copies of software and licenses for the software, that the web service uses during execution.
Ownership of such computing resources includes many expenditures of both time and money. In addition to the original acquisition costs of hardware, there are costs associated with servicing and upgrading the hardware, as well as future costs in maintaining or replacing the hardware. For software resources, there is original acquisition costs for licenses and there may be maintenance costs associated with such licenses. For software applications that may require a great deal of computing resources, such as web services that may be used by large numbers of people in parallel, the cost of hardware and software to support the software application may be large.
Cloud computing platforms, operated by a cloud operator, allow application owners to execute their software applications without owning the computing resources that the software applications uses to execute. A cloud computing platform includes a pool of computing resources, including hardware such as processors and storage devices. This pool of resources can be partitioned and can be allocated to execute a software application for an application owner. Some platforms partition the resources into virtual machines and each virtual machine can be instantiated and configured to execute a software application. Different virtual machines can be configured to execute different software applications. As a result, the cloud computing platform can be used to execute many different software applications on behalf of multiple application owners.
To execute software applications on the cloud platform, each application owner contracts with the cloud operator. The contracts between the application owner and the cloud operator define categories of virtual machines that are available for executing the software application—such as virtual machines with small, medium, and large amounts of hardware resources—and a billing rate associated with each of the virtual machines. Under the contract, the cloud operator is responsible for making the virtual machines available upon request by the application owner. The application owner is responsible for determining when to request additional resources, what category of resources to request, and when to release those resources back to the cloud computer platform. When the software application is executed and resources of the platform are requested and used by the software application, the cloud operator then bills the application owner for the time used on the requested resources at the rate set under the contract.